for National Geographic News
A mysterious set of monuments in Peru make up the oldest solar observatory in the Americas, according to a new study.
The 2,300-year-old Thirteen Towers of Chankillo were used for marking the sun's position throughout the year—an activity that was part of the sun-worshipping culture of the Inca, the study authors said.
The large stone towers are arranged in a line along a ridge near Chankillo, a walled hilltop ruin north of Lima.
"This is the oldest known example of landscape timekeeping in the Americas," said Ivan Ghezzi, lead author of the study and an archaeologist at the Pontifical Catholic University of Peru.
Ghezzi and archaeoastronomer Clive Ruggles of the University of Leicester, England, report their findings in tomorrow's issue of the journal Science.
The Inca civilization, which took power in the region around A.D. 1200, are known to have kept track of the positions on the horizon where the sun rose and set.
Writings by Spanish conquerors describe the Inca's methods of tracking these positions using sets of pillars.
But nearly all of these markers were apparently destroyed in a campaign to undermine the Inca Empire in the mid- to late 1500s.
"Astronomy was the backbone of the political and ideological system that supported the authority of the [Inca] rulers," Ghezzi said.
The Chankillo site appears to have been used only from about 300 B.C. to A.D. 1, meaning that an unidentified pre-Inca culture built the monuments.
Only one similar site in the Americas had been spotted so far, on the Island of the Sun in Lake Titicaca, on the border between Bolivia and Peru.
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